Various cases are known in relation to asthma, which include dyspeptic asthma, allergic asthma, atopic asthma, bronchial asthma, bacterial asthma, cardiac asthma and the like. Particularly, there are a great number of patients of bronchial asthma among these cases, so that studies have been made on agents or methods for its prevention and treatment. The action mechanism of anti-bronchial asthmatic agents is considered from two viewpoints, i.e. bronchiectasis and anti-inflammation, and many therapeutic and preventive agents has been developed. As the aforementioned bronchodilators, .beta..sub.2 -stimulators, methylxanthine and cholinolytic agents may be exemplified, and steroids and mediator inhibitors may be exemplified as the anti-inflammatory agents. However, since the current antiasthmatic agents have disadvantages in that the bronchodilators have strong side effects and the anti-inflammatory agents have low efficacy in therapeutic and preventive effects in comparison with other agents, great concern has been directed toward the development of excellent asthma-preventing and treating agents which can supplement both of these disadvantages.
In recent years, among these anti-inflammatory agents, mediator inhibitors such as PAF antagonists, thromboxane A.sub.2 (TXA.sub.2) antagonists/synthesis inhibitors and leukotriene (LTs) antagonists have been applied to asthma and their efficacy is being recognized. However, it has been reported that the therapeutic effect of these agents on asthma (medium or more improvement of the efficacy of agents) is approximately around 50% when used alone (Igakuno Ayumi 168 (4), 295 (1994) and Igakuno Ayumi 164 (4), 225 (1993)), suggesting that the efficacy is not sufficient because of the difference in the type of mediator which takes the main role in each patient of asthma.
Recently, some compounds capable of inhibiting a plurality of mediators have been reported (for example, an unexamined published Japanese patent application (Kokai) No. 4-154766). However, their effects are not sufficient from the viewpoint of oral absorbability, so that great concern has been directed toward the creation of clinically useful agents which can effect well-balanced inhibition of a plurality of mediators and also are excellent in oral absorbability.